A Simple Device for Making Successive Photomicrographic Records of 
Large Groups of Developing Organisms 1 
Sidney C. Hsiao, Walter K. Fujii, 
and Helen H. Fine 2 
In OUR analysis of the effect of ionizing radia- 
tion upon the cleavage of sea urchin zygotes 
we found it necessary to take successive photo- 
micrographs of a large number of eggs, in 
different samples, which had been exposed to 
graded doses of ionizing radiation (Hsiao and 
Daniel, I960). In order to estimate the rate 
of cleavage of the irradiated samples of ferti- 
lized eggs it is highly desirable to follow the 
cleavage of each egg in every sample and make 
photomicrographic records for later analysis. 
In other words, we need to take time-lapse 
pictures of the developing eggs subjected to 
different amounts of radiation so as to calcu- 
late the rate of cleavage and correlate it with 
dosage. After some preliminary trials we have 
put together, using commonly available ma- 
terials, a simple device capable of taking pho- 
tomicrographs repeatedly from the same field 
in a series of samples of irradiated eggs at 
specified time intervals. By lining up, accord- 
ing to time, prints made from each field, each 
egg can be identified and its cleavage followed 
from the first to the last frame in the series, 
and its rate of cleavage can be calculated. It 
occurs to us that investigators who have occa- 
sion to record developmental and other recur- 
rent phenomena may find this simple device 
useful. A brief description of its method of con- 
struction and manipulation is reported in this 
paper. 
PRINCIPLES OF CONSTRUCTION 
The simplest way to obtain a sequential rec- 
ord of a number of fertilized eggs after their 
exposure to irradiation or other treatment would 
1 Work supported by U. S. AEC contract AT (04-3) 
330. Hawaii Marine Laboratory contribution No. 189. 
2 Department of Zoology, University of Hawaii. 
Manuscript received February 6, 1962. 
be to place the eggs on the stage of the photo- 
micrographic instrument and take cinemato- 
graphic or time-lapse pictures. This requires 
one set of instruments for each sample exposed 
to one specific dose. The cost of equipment and 
the limitation of laboratory space would rule 
out all sample series of reasonable size. How- 
ever, if the samples are immobilized and the 
photomicrographic camera is brought over an 
exactly predetermined point in each sample to 
take time-lapse photomicrographs during the 
course of cleavage, it would be possible to make 
photographic records of a number of samples 
with one instrument. This can be done by: ( 1 ) 
Immobilizing samples of eggs contained in 
uniform-sized culture vessels, such as a culture 
cell on a 1- X 3 -inch micro slide, in a straight 
line on a stage supported by a steady stand 
independent of the photomicrographic camera, 
so that when the microscope moves no motion 
is transferred to the samples. ( 2 ) Using a pho- 
tomicrographic camera carriage made to move 
back and forth along a straight track placed 
parallel to the line of the immobilized sample 
cultures and adjusted to bring the microscope 
objective across the middle of the cultures. (3) 
Employing a series of uniform spacers (such 
as 1-inch rectangular bars for use with the 
1- X 3-inch micro slide containing samples of 
egg cultures), whose width equals the distance 
between the centers of the culture vessels of 
two neighboring samples, to stop the photo- 
micrographic camera carriage on the track each 
time the objective of the microscope reaches the 
center of a sample on the immovable stage. In 
this way a single photomicrographic camera 
can be used to photograph the eggs in the exact 
center of each sample culture vessel, and a 
series of the time-lapse photomicrographs is 
obtained for later analysis. 
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